As regards photosensitive polyimide, there have so far been known (a) the one prepared by coating a base plate with a mixture of 95-99 wt% of a polyamide acid type intermediate and 1-5 wt% of a dichromate, the coating being then irradiated with ultraviolet light, developed, if necessary, with hexamethylphosphoramide, and heated at 250.degree. C. (U.S. Pat. No. 3,623,870), and (b) the other one prepared by coating a base plate with a polyamide acid intermediate having a photosensitive group in the molecule, the coating being then cured in the same way as in the case of (a) (DE-OS No. 2308830).
However, the above-said composition (a) has difficulty of handling due to instability of said mixture and problem of insulating properties due to the remaining dichromate in the cured coating. Also, in the above-said (b), it was necessary to use pure materials (1) and (2) below in case, for example, where said photosensitive polyamide acid intermediate is synthesized by addition polycondensation or by polycondensation of an isomeric mixture of dicarboxylic acid dichloride derivatives represented by the following formula (1) having photosensitive groups ##STR1## (wherein R* is a group ##STR2## with the polyfunctional ring compound of the following formula (2), ##STR3## in order to increase the molecular weight of the resulting photosensitive polyamide acid intermediate. However, the above compounds (1) are difficult to purify because of the high viscousness and the moisture-labile character; in addition, compound (1) has a disadvantage of requiring a high cost for their production, which is practiced in many steps through the following reactions (3): ##STR4## (wherein R* is a group ##STR5##
The object of this invention is to provide an inexpensive composition of photosensitive polymer without any of such disadvantages of the prior arts and to provide cured film thereof formed on a supporting material.